Study of Imbibition Effect Using Temporal-Scale Analysis of Two-Phase Flow in a Tight Reservoir

Understanding the flow time scale in a tight reservoir has tremendous implications for theoretical studies and production system optimization. However, both the imbibition and dynamic coupling exert a significant effect on the fluid flow time scale and performance of the well during fracture and soaking, which is an effective way to develop a tight reservoir. In the present work, a multiple temporal scale flow model in a tight reservoir is established. A time scale analysis is conducted on the flow of fluid using Laplace transformation, finite-element method, and characteristic line method. The impact of imbibition and dynamic coupling on the temporal scale of the wellbore pressure is predicted. The results show that the wellbore pressure fluctuates when the time lag is considered or when the cross-flow coefficient from the matrix to the natural fracture is low. The imbibition is more evident for the case with higher capillary pressure and a tighter unstimulated region. The right-hand side peaks on the time scale diagram adequately reflect the water saturation propagation and fluid flow inside the unstimulated region. The effects of reservoir microstructure and imbibition on fluid flow in a porous medium may be better reflected by a time scale analysis. Results from this study can be helpful in optimizing the soaking duration, fracture scheme, and capillary pressure for the effective development of tight reservoirs.